1. Field of the Invention
This invention relates to fuel compositions which are effective for the prevention and control of engine deposits. In particular, this invention relates to fuel compositions containing aromatic esters of polyalkylphenoxyalkanols, poly(oxyalkylene) amines and di- or tri-carboxylic acid esters.
2. Description of the Related Art
It is well known that automobile engines tend to form deposits on the surface of engine components, such as carburetor ports, throttle bodies, fuel injectors, intake ports and intake valves, due to the oxidation and polymerization of hydrocarbon fuel. These deposits, even when present in relatively minor amounts, often cause noticeable driveability problems, such as stalling and poor acceleration. Moreover, engine deposits can significantly increase an automobile's fuel consumption and production of exhaust pollutants. Therefore, the development of effective fuel detergents or "deposit control" additives to prevent or control such deposits is of considerable importance and numerous such materials are known in the art.
For example, aliphatic hydrocarbon-substituted phenols are known to reduce engine deposits when used in fuel compositions. U.S. Pat. No. 3,849,085, issued Nov. 19, 1974 to Kreuz et al., discloses a motor fuel composition comprising a mixture of hydrocarbons in the gasoline boiling range containing about 0.01 to 0.25 volume percent of a high molecular weight aliphatic hydrocarbon-substituted phenol in which the aliphatic hydrocarbon radical has an average molecular weight in the range of about 500 to 3,500. This patent teaches that gasoline compositions containing minor amounts of an aliphatic hydrocarbon-substituted phenol not only prevent or inhibit the formation of intake valve and port deposits in a gasoline engine, but also enhance the performance of the fuel composition in engines designed to operate at higher operating temperatures with a minimum of decomposition and deposit formation in the manifold of the engine.
Similarly, U.S. Pat. No. 4,134,846, issued Jan. 16, 1979 to Machieder et al., discloses a fuel additive composition comprising a mixture of (1) the reaction product of an aliphatic hydrocarbon-substituted phenol, epichlorohydrin and a primary or secondary mono- or polyamine, and (2) a polyalkylene phenol. This patent teaches that such compositions show excellent carburetor, induction system and combustion chamber detergency and, in addition, provide effective rust inhibition when used in hydrocarbon fuels at low concentrations.
Amino phenols are also known to function as detergents/dispersants, antioxidants and anti-corrosion agents when used in fuel compositions. U.S. Pat. No. 4,320,021, issued Mar. 16, 1982 to R. M. Lange, for example, discloses amino phenols having at least one substantially saturated hydrocarbon-based substituent of at least 30 carbon atoms. The amino phenols of this patent are taught to impart useful and desirable properties to oil-based lubricants and normally liquid fuels.
Similarly, U.S. Pat. No. 3,149,933, issued Sep. 22, 1964 to K. Ley et al., discloses hydrocarbon-substituted amino phenols as stabilizers for liquid fuels.
U.S. Pat. No. 4,386,939, issued Jun. 7, 1983 to R. M. Lange, discloses nitrogen-containing compositions prepared by reacting an amino phenol with at least one 3- or 4-membered ring heterocyclic compound in which the hetero atom is a single oxygen, sulfur or nitrogen atom, such as ethylene oxide. The nitrogen-containing compositions of this patent are taught to be useful as additives for lubricants and fuels.
Nitro phenols have also been employed as fuel additives. For example, U.S. Pat. No. 4,347,148, issued Aug. 31, 1982 to K. E. Davis, discloses nitro phenols containing at least one aliphatic substituent having at least about 40 carbon atoms. The nitro phenols of this patent are taught to be useful as detergents, dispersants, antioxidants and demulsifiers for lubricating oil and fuel compositions.
Similarly, U.S. Pat. No. 3,434,814, issued Mar. 25, 1969 to M. Dubeck et al., discloses a liquid hydrocarbon fuel composition containing a major quantity of a liquid hydrocarbon of the gasoline boiling range and a minor amount sufficient to reduce exhaust emissions and engine deposits of an aromatic nitro compound having an alkyl, aryl, aralkyl, alkanoyloxy, alkoxy, hydroxy or halogen substituent.
More recently, certain poly(oxyalkylene) esters have been shown to reduce engine deposits when used in fuel compositions. U.S. Pat. No. 5,211,721, issued May 18, 1993 to R. L. Sung et al., for example, discloses an oil soluble polyether additive comprising the reaction product of a polyether polyol with an acid represented by the formula RCOOH in which R is a hydrocarbyl radical having 6 to 27 carbon atoms. The poly(oxyalkylene) ester compounds of this patent are taught to be useful for inhibiting carbonaceous deposit formation, motor fuel hazing, and as ORI inhibitors when employed as soluble additives in motor fuel compositions.
Poly(oxyalkylene) esters of amino- and nitrobenzoic acids are also known in the art. For example, U.S. Pat. No. 2,714,607, issued Aug. 2, 1955 to M. Matter, discloses polyethoxy esters of aminobenzoic acids, nitrobenzoic acids and other isocyclic acids. These polyethoxy esters are taught to have excellent pharmacological properties and to be useful as anesthetics, spasmolytics, analeptics and bacteriostatics.
Similarly, U.S. Pat. No. 5,090,914, issued Feb. 25, 1992 to D. T. Reardan et al., discloses poly(oxyalkylene) aromatic compounds having an amino or hydrazinocarbonyl substituent on the aromatic moiety and an ester, amide, carbamate, urea or ether linking group between the aromatic moiety and the poly(oxyalkylene) moiety. These compounds are taught to be useful for modifying macromolecular species such as proteins and enzymes.
U.S. Pat. No. 4,328,322, issued Sep. 22, 1980 to R. C. Baron, discloses amino- and nitrobenzoate esters of oligomeric polyols, such as poly(ethylene) glycol. These materials are used in the production of synthetic polymers by reaction with a polyisocyanate.
U.S. Pat. No. 4,859,210, issued Aug. 22, 1989 to Franz et al., discloses fuel compositions containing (1) one or more polybutyl or polyisobutyl alcohols wherein the polybutyl or polyisobutyl group has a number average molecular weight of 324 to 3,000, or (2) a poly(alkoxylate) of the polybutyl or polyisobutyl alcohol, or (3) a carboxylate ester of the polybutyl or polyisobutyl alcohol. This patent further teaches that when the fuel composition contains an ester of a polybutyl or polyisobutyl alcohol, the ester-forming acid group may be derived from saturated or unsaturated, aliphatic or aromatic, acyclic or cyclic mono- or polycarboxylic acids.
U.S. Pat. Nos. 3,285,855, and 3,330,859 issued Nov. 15, 1966 and Jul. 11, 1967 respectively, to Dexter et al., disclose alkyl esters of dialkyl hydroxybenzoic and hydroxyphenylalkanoic acids wherein the ester moiety contains from 6 to 30 carbon atoms. These patents teach that such esters are useful for stabilizing polypropylene and other organic material normally subject to oxidative deterioration. Similar alkyl esters containing hindered dialkyl hydroxyphenyl groups are disclosed in U.S. Pat. No. 5,196,565, which issued Mar. 23, 1993 to Ross.
U.S. Pat. No. 5,196,142, issued Mar. 23, 1993 to Mollet et al., discloses alkyl esters of hydroxyphenyl carboxylic acids wherein the ester moiety may contain up to 23 carbon atoms. This patent teaches that such compounds are useful as antioxidants for stabilizing emulsion-polymerized polymers.
Commonly assigned U.S. Pat. No. 5,407,452, issued Apr. 18, 1995, and corresponding International Application Publication No. WO 95/04118, published Feb. 9, 1995, disclose certain poly(oxyalkylene) nitro and aminoaromatic esters having from 5 to 100 oxyalkylene units and teach the use of such compounds as fuel additives for the prevention and control of engine deposits.
Similarly, commonly assigned U.S. Pat. No. 5,427,591, issued Jun. 27, 1995, and corresponding International Application Publication No. WO 94/14926, published Jul. 7, 1994, disclose certain poly(oxyalkylene) hydroxyaromatic esters which are useful as fuel additives to control engine deposits.
In addition, commonly assigned U.S. Pat. No. 5,380,345, issued Jan. 10, 1995, and corresponding International Application Publication No. WO 95/15366, published Jun. 8, 1995, disclose certain polyalkyl nitro and aminoaromatic esters useful as deposit control additives for fuels. Moreover, commonly assigned International Application Publication No. WO 95/11955, published May 4, 1995, discloses certain polyalkyl hydroxyaromatic esters which are also useful as deposit control fuel additives.
Poly(oxyalkylene) amines are also well known in the art as fuel additives for the prevention and control of engine deposits. For example, U.S. Pat. No. 4,191,537, issued Mar. 4, 1980 to R. A. Lewis et al., discloses a fuel composition comprising a major portion of hydrocarbons boiling in the gasoline range and from 30 to 2000 ppm of a hydrocarbyl poly(oxyalkylene) aminocarbamate having a molecular weight from about 600 to 10,000, and at least one basic nitrogen atom. The hydrocarbyl poly(oxyalkylene) moiety is composed of oxyalkylene units selected from 2 to 5 carbon oxyalkylene units. These fuel compositions are taught to maintain the cleanliness of intake systems without contributing to combustion chamber deposits.
U.S. Pat. No. 5,112,364, issued May 12, 1992 to Rath et al., discloses gasoline-engine fuels which contain small amounts of a polyetheramine and/or a polyetheramine derivative, wherein the polyetheramine is prepared by reductive amination of a phenol-initiated or alkylphenol-initiated polyether alcohol with ammonia or a primary amine.
U.S. Pat. No. 4,247,301, issued Jan. 27, 1981 to Honnen, discloses hydrocarbyl-substituted poly(oxyalkylene) polyamines, wherein the hydrocarbyl group contains from 1 to 30 carbon atoms and the polyamine moiety contains from 2 to 12 amine nitrogen atoms and from 2 to 40 carbon atoms. This patent teaches that the additives may be prepared by the reaction of a suitable hydrocarbyl-terminated polyether alcohol with a halogenating agent, such as HCl or thionyl chloride, to form a polyether chloride, followed by reaction of the polyether chloride with a polyamine to form the desired poly(oxyalkylene) polyamine. This patent also teaches at Example 6 that the polyether chloride may be reacted with ammonia or dimethylamine to form the corresponding polyether amine or polyether dimethylamine.
Aromatic di- or tri-carboxylic acid esters have also been described for use in fuel additive compositions. For example, U.S. Pat. No. 5,405,418, issued Apr. 11, 1995 to Ansari et al., discloses a fuel additive composition comprising (a) a fuel-soluble aliphatic hydrocarbyl amine wherein the hydrocarbyl group has a number average molecular weight of about 700 to 3,000, (b) a polyolefin polymer of a C.sub.2 to C.sub.6 monoolefin wherein the polymer has a number average molecular weight of about 350 to 3,000 and (c) an aromatic di- or tri-carboxylic acid ester. This patent further teaches that the above fuel additive composition provides excellent valve sticking performance while maintaining good control of engine deposits.
In addition, U.S. Pat. No. 5,004,478, issued Apr. 2, 1991 to Vogel et al., discloses a motor fuel for internal combustion engines which contains an additive comprising (a) an amino- or amino-containing detergent and (b) a base oil which is a mixture of (1) a polyether based on propylene oxide or butylene oxide and having a molecular weight of not less than 500 and (2) an ester of a mono carboxylic or polycarboxylic acid and an alkanol or polyol.
Aromatic esters of polyalkylphenoxyalkanols are also known in the art as fuel additives for the prevention and control of engine deposits. Thus, commonly assigned U.S. Pat. No. 5,618,320, issued Apr. 8, 1997 to Cherpeck et al., discloses hydroxy, nitro, amino and aminomethyl substituted aromatic esters of polyalkylphenoxyalkanols which are useful as additives in fuel compositions for the control of engine deposits, particularly intake valve deposits.
In addition, commonly assigned U.S. Pat. No. 5,749,929, issued May 12, 1998 to Cherpeck et al., and corresponding International Application Publication No. WO 97/43357, published Nov. 20, 1997, discloses a fuel additive composition comprising aromatic esters of polyalkylphenoxyalkanols in combination with poly(oxyalkylene) amines, which is useful for the control of engine deposits.